The present invention relates to an improvement of an under seal for a linear guide apparatus used for machine tools and industrial machinery.
A conventional under seal for a linear guide apparatus is of an insertion type which is proposed in U.S. Pat. No. 4,921,358 applied for by the present applicant. The conventional linear guide apparatus to which the under seal is applied is of such a type that a slider is fitted into an axially extending guide rail so as to be movable in the axial direction, the guide rail having ball rolling grooves axially extending in both side surfaces of the guide rail. The slider includes a slider main body and end caps fitted to the end portions of the slider main body. In the inner side surfaces of the slider main body are provided ball rolling grooves confronting the ball rolling grooves of the guide rail. On a thick wall portion of each of sleeve portions of the slider main body are provided ball return paths, which are through holes extending in parallel with these ball rolling grooves. On the other hand, each end cap has semiarcuate curved paths that allow the ball return paths to communicate with the ball rolling grooves, respectively. Thus, the slider can move relative to the guide rail in the axial direction through the circulation of a plurality of rolling balls loaded to both the ball rolling grooves confronting each other, the ball return paths, and the curved paths.
Each end cap of the linear guide apparatus has a seal holding groove formed in a surface fitting with the slider main body, ends of the under seal being inserted into the seal holding groove. Further, each sleeve portion of the slider main body has an under seal receiving stepped portion formed in the lower surface thereof and receding from the lower face of the slider main body.
As shown in FIG. 7, the under seal includes a lip portion and a rubber body. The lip portion slidingly contacts a surface of the guide rail. The rubber body, fixed to a core bar, has resilient projections 46 projected upward at both ends of the core bar in the axial direction thereof. The under seal is fitted into the under seal receiving stepped portions of the slider main body by inserting both ends of the under seal into the seal holding grooves of each end cap. As a result of this design, the resilient projections projected at both ends of the under seal are pressed onto the surfaces of the seal holding grooves, thereby allowing the under seal to be held in the seal holding grooves with the resilient force. The under seal is easy to be fixed to the end cap at once.
However, the aforementioned conventional under seal for the linear guide apparatus attaches importance to fixing the under seal so as to prevent the under seal from falling away from the slider. Accordingly, it is difficult for an unskilled person to attach the under seal properly to the end caps, and this has led to the problem of deteriorating the sealing efficiency due to improper attachment.
Incidentally, a small margin of adjustment (play) is provided between the seal holding groove of each end cap and the corresponding end portion of the under seal that is inserted into the holding groove so that the user can attach the under seal to the end caps with ease. In the case where the slider is shipped separately from the guide rail so that the slider will be assembled to the guide rail by the user or in a like case, the slider may be displaced from the guide rail by the margin of adjustment. As a result, a clearance, although very small, in some cases, may be produced between the lip portion of the under seal and the surface of the guide rail which must tightly contact with each other.